Level 1, Tourism House | 40 Blackall Street, Barton ACT 2600 | PO Box 5367, Kingston ACT 2604 | resistance. ability ofthemoth torapidlydevelop by mild,drywinter conditionsandthe markedly inthepastdecade, exacerbated severity ofDBMoutbreaks haveincreased In someregions, thefrequency and per cent. responsible foryieldlossesofupto80 flower headsandpods,canbe DBM larvaefeedonplantfoliage,stems, forage crops. pest ofcanola,brassicavegetablesand Diamondback (DBM)isanoccasional Crop monitoringfrom Julyonwards iskeytomakingeffective decisionsforcontrolling diamondbackmoth. but seriocanolachallenge Diamondback othissporadc We and Southern FACT SHEET Diamondback Moth JulY 2013 Key Points – – – – – – – – – – – – – – and mustbeobserved. windrowing are thesame, periods before harvestor Spray applicationwithholding days tocontrol DBM. two spraysappliedwithinseven High-risk situationsmayrequire groups betweenyears. decisions androtate insecticide Use thresholds toguidespray isamajorconcern. Resistance tocommonlyused onwards. monitor crops from mid-July The keytoDBMcontrol isto with mildwinters. regions, particularlyinseasons more frequent andsevere insome DBM outbreaks havebecome found inallgrain-growing regions. be aseriouspestofcanolaandis Diamondback moth(DBM)can tern region stern

PHOTO: DAFWA and haveadark headinthefirsttwo The larvaegothrough fourgrowth stages yellowish-green andtapered atboth ends. DBM larvaegrow to12mmlong,are pale in length. are paleyellow, ovalandabout0.5mm wings are foldedoverthebody. width downthecentre ofthebackwhen stripeof uneven white diamond-patterned long andgrey-brown incolour. Theyhavea DBM (Plutellaxylostella)are 10millimetres About diamondbackmoth by asilkenthread. When DBMlarvaeare disturbedtheywillwriggle,andmaydrop from theplant s T +61 2 6166 4500 | F +61 2 6166 4599 | has died. winds, especially whentheirhostplant can migratelong distancesonprevailing a crop. However, outsidethecrop, they the night,butusuallydonotfly farwithin DBM are activeatduskandthroughout before emergingasanadultmoth. starts off green incolour, brown turning isvisibleinsidethecocoonand usually ontheundersideofleaves.The Mature larvaespingauze-likecocoons, often drop from aplantonsilkenthread. stages. Theywrigglewhendisturbedand E [email protected] | W www.grdc.com.au

30 per 10 sweeps 50 per 10 sweeps 200 per 10 sweeps > 50 per 10 sweeps >100 per 10 sweeps DBM larvae threshold Diamondback are so named for so named are Diamondback moths patternthe distinctive diamond-shaped on their back. weather for the pest to complete three or weather for the pest to complete three four generations. Sampling should be carried out at a minimum of four separate locations within to gain an estimate each canola crop of DBM numbers and how they vary the paddock. throughout sets of 10-sweep samples (that is, Two 10 consecutive sweeps with a sweepnet) should be taken at each of the four locations, giving a total of eight 10-sweep samples. Empty the contents of each set of 10 sweeps onto a white or light- surface, for example the bonnet coloured of a white vehicle, and count the number of larvae. Note the sizes of the DBM larvae and the presence of other . of other insects. larvae and the presence If no or low numbers of DBM are should be monitored detected the crop again in two weeks. at least three When DBM numbers increase, estimates of larval density over 12 days are needed to determine how the population is changing. On each occasion, eight or 10-sweep samples should be taken more the crop. throughout Cool, wet, windy weather can reduce DBM numbers. Numbers of larvae can by beneficial insects and also be reduced diseases. Y N N N N PHOTO: KEVIN WALDEN

Moisture stress

by crop stage guidelines by crop able 1 DBM threshold T Mid to late-flowering* Pre-flowering Early to mid-flowering* maturation*Pod Crop stage Monitoring for infestations using an should be monitored Crops insect sweepnet at the first sign of the damage and at intervals throughout to mid-July through season from growing late spring/early summer. quickly if likely to increase Numbers are DBM infest canola early in the season and if warm of prolonged chance is a strong there upper surface intact, which creates a see- upper surface intact, which creates effect. window through Larvae can be found at any stage of a development, with their canola crop’s in the lead- numbers often increasing up to flowering. Canola can tolerate crop considerable leaf damage before severe However, yield is affected. infestations of DBM larvae can cause complete defoliation and substantial yield losses. increasing As flowering progresses, numbers of larvae move to the floral buds, onflowers and pods. Large larvae may feed small young pods. plants during the Damage to mature late spring by rising populations of DBM often causes visible scarring of the outer in any results pod walls, but this rarely economic loss. oisture stress not listed for these growth stages because moisture stressed crops are more susceptible to insect damage. A lower more are crops stressed stages because moisture not listed for these growth stress * Moisture expected. may be used if extended dry periods are threshold

substantial yield losses. affected. However, severe infestations of DBM larvae can cause complete defoliation and larvae can cause complete defoliation infestations of DBM severe However, affected. Canola can tolerate considerable leaf damage from DBM larvae before crop yield is crop DBM larvae before considerable leaf damage from Canola can tolerate wet, warm weather. outbreak of insect fungal diseases during outbreak understood. One factor may be the of the leaves and often cause holes with the and the reason for this is only partially and the reason traces. Older larvae feed on the underside DBM populations can suddenly crash larvae appears as characteristic pale-white crop at any one time. crop The damage caused by newly hatched may be present in a in a all life stages of DBM may be present canola, but this does not happen in all years. considerable overlap in generations and considerable overlap in generations and DBM larvae can cause extensive damage to n warm weather there is often is often In warm weather there Damage than 100 days. whereas at 12°C the life cycle takes more at 12°C the life cycle takes more whereas of 28°C the DBM life cycle takes 14 days, For example, at a constant temperature For example, at a constant temperature weather and slower in cool weather. depends on temperature. It is faster in warm depends on temperature. The rate of development from eggs to mothsto eggs from development of rate The the undersides of leaves. the plant surface and are usually found on the plant surface and are The next three stages of the larvae feed on The next three leaf tissue. the first stage of the larvae burrow into the the first stage of the larvae burrow leaves. Eggs hatch after four to six days and along the leaf vein on both sides of plant in their lifetime, singly or in small clusters Female moths can lay more than 100 eggs Female moths can lay more alternate hosts into canola crops. fly from such In autumn to early winter DBM fly from the ‘green bridge’ and DBM populations. the ‘green and Lincoln weed. Summer rainfall increases and Lincoln weed. Summer rainfall increases summer brassica weeds such as wild survive between growing seasons on DBM survive between growing Life cycle are controlled. stages thatsurvive thefirstapplication this strategywill ensure thatDBMinlife Under typicaltemperature conditions yield losses. give adequatecontrol oflarvaeandreduce applications (fivetosevendays apart)can a quickresponse withtwospray densities are atthespraythreshold, Once sweepnettingindicatesDBMlarval one seasontothenext. betweeninsecticidegroupsalternate from only whenthresholds are exceededand to thesenewerinsecticides,sprayforDBM To reduce theriskofresistance developing three effective insecticidegroups. available), growers cannowchoosefrom ( the biologicalinsecticideBacillusthuringiensis and Success for DBMcontrol incanola:Affirm In 2012twonewinsecticideswere registered several agriculturalindustries. application oftheseinsecticidesacross This isaresult ofover-reliance andpoor to manyinsecticidesincludingsynthetic DBM hasdevelopedwidespread resistance Control measures larvae exceeds30in10sweeps. be considered iftheaverage numberof in pre-flowering crops, sprayingshould periods are anticipated.For example, threshold maybeusedifextended dry susceptible toinsectdamageandalower Moisture-stressed crops are more increase further. 3mm long)indicatesnumbersare likelyto A highnumberofsmalllarvae(lessthan a guideforspraydecisions. significant yieldloss. Table 1showslevelsas increasing numbersofDBMwithoutany As canoladevelops,itcantolerate threshold levels. seasonal conditionsalsoinfluencesspray the threshold. Variation inregional and the higherspraycost, economic threshold and,conversely, The higherthegrainprice,lower spraying willprovide aneconomicreturn. considered whendecidingwhether and costofsprayingwillneedtobe price The crop growth stage,grain to 200larvaeper10sweeps. spraying. Economicthresholds varyfrom 30 There isnosimple‘onefigure fitsall’for When toact Bt) (arangeofregistered products are

and organophosphates. ® Neo(Group 5).Together with ® roup 6) (Group 6)

PHOTO: DAFWA a canopy crop isimportant asabout 20 Achieving good chemicalpenetrationinto registration detailsontheproduct label. a harvestevent.Usersmustabideby same, becausewindrowing isconsidered before harvestandatwindrowing are the should notethatwithholdingperiods vary withchoiceofchemical. Growers The periodbetweenapplications may are controlled. and larvaethatsurvivethefirstapplication spray strategytherefore ensures DBMeggs compared withunsprayedcanola.Atwo- little impactonthedamagecausedwhen August onrisingpopulationsofDBMhad grainbelt foundasinglesprayinmid- Research inWesternAustralia’s northern is warranted. occurred, andthatasecond spray indicate thatanewhatchingoflarvaehas numbers ofonlyverysmalllarvaewould poor coverageand/orresistance. Higher that thefirstspraywasineffective, dueto of survivinglargelarvaewouldindicate second sprayisapplied.Highnumbers determine survivingnumbersbefore a the effectiveness ofthespray andto days afterthefirstspraytoassess should beundertakenthree tofive Sweepnet samplingofcanolacrops leaf. Pupaestartoutgreen,brown thenturn incolourbefore hatchingoutasadultmoths. DBM pupaevisiblethrough thegauze-likecocoononundersideofadamagedcanola

achieved byduskapplication. by ultravioletlight,sothebestresults are less than5mminlength.Btisbroken down are usedthemajorityoflarvaeshouldbe disruptive tobeneficialinsects,suchasBt, Where ‘soft’chemicalsthat are less and spraypenetrationtolowerleaves. droplet sizetoachievegood leafcoverage effective inproviding waterratesand ha ofwater)applicationscanbeequally based (flat-fan11015nozzleswith50L/ litres perhectare ofwater)andground- conditions, aerial(CP90nozzleswith30 Trials showthat undergoodspraying lower plantcanopy. per centofDBMlarvaeare foundonthe eggs, a range of spiderswillfeed onDBMeggs, lacewings, several predacious bugsand Predators such asbrown andgreen fail todevelop. inside. TheparasitisedDBMlarvaeorpupae where thedevelopingwasplarvaefeed or pupae(dependingonthewasp species) wasps laytheireggsinsideDBM larvaeand/ collaris andOomyzussokolowskii . These semiclausum, ApantelesippeusDiadromus These includetheparasiticwaspsDiadegma A numberofbeneficialinsectsattackDBM. Integrated management larvae and pupae. Often these insects can more information Useful Resources be enough to prevent economic damage to canola crops. Greg Baker DBM Development Calculator SARDI (Victorian Department of Primary Beneficial insects should be encouraged 08 8303 9544 Industries) by better targeting and reducing insecticide [email protected] www.dpi.vic.gov.au/agriculture/pests- applications. A fungus, Zoophthera diseases-and-weeds/pest-insects/ Peter Mangano radicans, can cause a 90 per cent reduction ag0512-diamondback-moth/sampling- DAFWA in DBM larvae numbers. The fungus favours plan/further-information 08 9368 3753 rainfall, humidity and warm temperatures. Beneficial Insects: The Back Pocket [email protected] Diseased larvae become yellowish, sluggish Guide and swollen before dying. Dead larvae are Svetlana Micic www.grdc.com.au/GRDC-BPG- white, brittle, flat, covered with fungus and DAFWA BeneficialInsects-SW attached to the plant leaves. 08 9892 8591 [email protected] Acknowledgements: Summer weeds and self-sown canola Greg Baker, Peter Mangano, Dr Paul Umina provide a ‘green bridge’ on which DBM Svetlana Micic, Dr Paul Umina cesar can survive over summer. Controlling these 03 9349 4723 weeds within districts to be sown to canola GRDC Project Code [email protected] is an important management control to DAS00094 restrict the potential DBM risk.

Frequently Asked Questions

When is the best time to look for DBM? late-flowering and most pods are formed the average number Start looking for DBM larvae and damage to leaves when canola of DBM larvae needs to exceed 100 larvae per 10 sweeps to crops begin flowering. Check crops regularly. Monitoring is the key warrant spraying. to assessing the risk of a DBM outbreak. Are withholding periods before harvest the same as for How do I know the extent of the infestation? windrowing? Crops should be monitored with a sweepnet to gain an idea Yes. Windrowing is considered a harvest event. of the prevalence of, and changes in, DBM populations and stages of development, as per the protocol outlined above in What is the best control option? ‘Monitoring for infestations’. No single registered DBM treatment completely removes DBM. When do I spray? About 20 per cent of DBM larvae are found on the lower part of the As canola develops it can tolerate increasing numbers of DBM canola canopy, which makes good spray coverage critical. When without any significant yield loss. In early flowering canola, if more large outbreaks have occurred, two spray applications five to seven than 10 larvae are found in 10 sweeps then a major outbreak days apart have given significantly greater control of caterpillars and could develop. Continue crop monitoring. During early to mid- reduced yield loss. This two-spray strategy ensures that DBM eggs flowering and pod formation if average numbers of 50 or more and caterpillars that survive the first application are also controlled. larvae per 10 sweeps are found (and the numbers fail to decline Use a sweepnet to sample crops three to five days after the first after seven to 12 days) then spraying should be considered. spray to assess its effectiveness and determine surviving numbers. This threshold increases later in the season. When crops are at This will help determine if a second spray is needed.

Disclaimer Any recommendations, suggestions or opinions contained in this publication do not necessarily represent the policy or views of the Grains Research and Development Corporation. No person should act on the basis of the contents of this publication without first obtaining specific, independent, professional advice. The Corporation and contributors to this Fact Sheet may identify products by proprietary or trade names to help readers identify particular types of products. We do not endorse or recommend the products of any manufacturer referred to. Other products may perform as well as or better than those specifically referred to. The GRDC will not be liable for any loss, damage, cost or expense incurred or arising by reason of any person using or relying on the information in this publication. CAUTION: RESEARCH ON UNREGISTERED USE Any research with unregistered or of unregistered products reported in this document does not constitute a recommendation for that particular use by the authors or the authors’ organisations. All pesticide applications must accord with the currently registered label for that particular pesticide, crop, pest and region. Copyright © All material published in this Fact Sheet is copyright protected and may not be reproduced in any form without written permission from the GRDC. produced by www.coretext.com.au